Band-brake adjusting mechanism



Nov. 2, 1937. J. YOXALL 2,098,125

BAND BRAKE ADJUSTING MECHANISM Filed April 10, 1935 2 Sheets-Sheet 2 Patented Nov. 2, 1937 I UNITED STATES PATENT OFFICE BAND-BRAKE ADJUSTING MECHANISM Joseph Yo'xall, Deganwy, North'Wales, assignor to Propello Inventions Limited, London,- England, a British company Application April 10, 1935, Serial No. 15,671 In Great Britain June 29, 1934 10 Claims. (01. 188-795) The present invention relates to mechanism for is effected by means pressing against links in each automatically taking up wear in band-brakes. of them; these means may be manually operated, The present invention has for its object to proor operated by a pedal. or as shown, by hydraulic vide an improved construction of adjusting mechmeans. The hydraulic means comprise a cylinanism. der 64 into which pressure-fluid can be admitted 6 According to the present invention self-adfrom a conduit I05 by way of orifices l0 and II justing mechanism for taking up wear inbandwhen a rotary valve member 43 constituting the brakes comprises a drum, a brake-band, mem conduit is turned so that the orifices l0 and ll bers movable to apply said brake-band on said coincide. When pressure-fluid is admitted into 10 drum, a bipartite member capable of alteration cylinder 64 it exerts pressure against two pistons 10 in length by screwed adjustment of its parts, two I06, I01 therein, which pistons are in permaaxially separated self-lapping coil springs of opnent contact with rollers I00, I00 each attached posite hand mounted one on each part of said to one member of the two toggle systems. A bipartite member and serving, when the brakespring IIO maintains contact between pistons band becomes worn a predetermined amount to I06, I01 and rollers I00, I00. 15 produce alteration in length of said bipartite Attention is now particularly directed to the member, upon fully applying and releasing the right-hand toggle-system shown in Figure l.

brake-band. which system is also shown in end elevation in In order that the invention may be readily Figure 2, and in disassembled condition in Figunderstood, the same will now be described with ure 3. 20

reference to the accompanying drawings which This toggle system is constituted by three eleillustrate, by way of example, one embodiment ments, viz., a long arm III, and two short struts thereof. II2, III. Ann. I II actually consists of two plates In the drawings: III, II Ia, riveted together by means 0! bridge Figure 1 shows partly in cross-section and pieces I, lit: holes are drilled in the plates 25 partly in elevation the adjusting mechanism as II I, la to accommodate a pin H8 by which applied to an external contracting band-brake; the a III is p ly a h e in a rooved Figure 2 is a cross section taken along line 2-2 member H9 fixed to the casing 3. Strut III conof Figure 1. sists of a short steel wedge-shaped member, one Figs 3, 4, 5, 6 and I are perspective views 01' end, I20, of which is forked so as to fit upon 30 various disassembled parts of the right-hand bridge piece I I5 and be capable of slight swinging brake applying unit seen in Fig. 1; and movement thereon. Strut II! is constituted by Fig.8 is a perspective view of the brake bands three elements "I, I22, I22 of which I2I is a and some associated parts illustrating the relaflattened steel member having one endi24 roundtive position of such bands. ed to form a bearing surface and provided with Reference numeral 3 indicates a casing surcheeks I25, I25 adapted to prevent the end I24 rounding the brake-band assembly, 53 is an anfr m pp ng laterally from a shaped bearing nulus or drum to be braked, and 60, ii are two surface termed on segmental member I04 against brake-bands encircling the said drum is, The which member I2I bears. The other end I20 two brake-bands each extend around the drum 53 member tubular and 18 p ed w t 8 40 and are situated side by side thereon, the band coiled sp g I21 gripped thereto by screw I20, 0| being attaphed to two relatively movable segand adapted to co-operate with a surface of the mental members I02, ill by means of rivets. As r p ndingly shaped element I22. This eleseen in Figure 1 brake-band so is to the rear of meat I22 comprises a rod having at one end a brake-band 0|, the former being visible only at portion I20 of reduced diameter adapted to flt 45 the gap between members I02, I. Desirably the tubular end I20 01' member HI, and formed the brake-lining proper BI is mounted upon a at its other end III with aninternal screw-thread flexible met lli strip in, hi 1 itself riveted III. Over theend I30 there is slipped a tubular to the members I02, I04. Similarly, brake-band member "2 provided with wings I. nd 8| is mounted upon metallic strip m, attached with a coil sp s I" r pp d y a screw 50 at its ends to segmental members 22, I00. Apmounted in wing I32, member I32 being retained plication oi the two brake-bands 00. ii, to the in position on element I22 by a sprung-on ring drum It is eirected by means of two toggle sys- Ill fitting inagroove therein. Element I22 comtems or units, one for each band. It is to be prises a castor I20 carrying the roller I02, alexplained that the actuation of the two toggles ready reierred to, and provided with a threaded 55 2 aooam extension I33 adapted to be screwed into the screw-thread I3I in member I22.

It will be noted that coil springs I30, I21 are of opposite hand, spring I35 being adapted to 5 grip upon the surface of member I22 by a selflapping action when (in the assembled form of the device shown in Figure 1 as viewed from above) member I32 is turned clockwise relatively to member I22, and spring I21 exerting a gripping action on member I22 when attempt is made to turn it anti-clockwise relatively to member I2 I as viewed in Figure 2.

In Figure 1 the right-hand toggle is shown in assembled form, and in the condition in which 5 the brake-band is fully applied after it has undersone some wear.

It will be seen that in order to apply the band 30 fully it has been necessary for piston I01 to shift members H2, H3 of the toggle into a position in which they are nearly coincident with the third member III of the toggle, the movement of members H2, 3 being limited by a stop I43 since brake band III is shown in Fig. l as fully applied (and being also substantially as worn), it is to be observed that member I23 of the brake mechanism is hard up against stop I43 whfchirin the'iorm of a bar'held between plates III, Illa: such an amount of movement of the piston, and of roller I09 can only .ocour when the brake-band has worn (since, if the band is not worn then the same becomes fully applied on to its drum 53 by only a slight rightward movement of member I23, in which event said member does not reach stop I43), and when this movement takes place wing I33 is caused to strike against plate Illa and turn member I32 on member I22, thus causing wing I34, which has by this time passed to the right of plate IIIa as seen in Figure 2, to rise, so that 0 upon release of the brake-band and movement of roller I09 and related parts to the left, it is wing I34 that is caused to strike against plate Illa and turn member I32. The first turning movement of member I32 (caused by a full rightward movement of roller I09 with the brakeband worn) causes member I32 to turn freely on member I22 in an anticlockwise direction-as viewed in Figure 2, coil spring I35 allowing this free movement and coil spring I21 preventing member I22 from following the movement of member I32; the second turning movement of member I32 (caused by the return of roller I00 upon release of the brake-band) causes coil spring I35 to bind on the surface of member I22 and turn it in a clockwise direction, as viewed in Figure 2, said movement causing coil spring I21 to release its grip on member I22. This turning movement causes member I22 to be screwed a slight distance along threaded extension I33 whereby the strut II2 of the toggle is lengthened and wear in the brake-band is compensated for. If piston I01 and roller I03 are moved repeatedly to and fro, when the brake-band is worn, strut H2 is lengthened slishtly at each return moveas ment until the brake-band has been adjusted to such a tightness that upon the. normal movement of roller I00 the band is fully applied and member I32 is not caused to reach a position during full application of the brake in which wing I33 strikes plate Illa. When this condition is reached, no further adjustment of the brakeband takes place, but immediately the same wears and permits member I32 to move rightwardly a sufficient distance to allow wing I33 to strike plate Illa, then automatic adjustment takes place.

It may be noted that if a new brake band is inserted in a band-brake according to the invention, the same may be automatically ad- 5 iusted to exactly the right tension by merely applying and releasing the brake a number of times.

The construction of the left-hand toggle mechanism shown in Figure l is very similar to that m of the right-hand toggle except that the roller I03 is attached to arm I40 of the toggle, whilst the relative position thereof to that of elements I, I42 (corresponding to elements H2, 3 of the right-hand toggle) is reversed. element III is being pivotally anchored at Illa, to the easing 3. It is to be observed that when brake band 00 is slack on drum I3, roller I00 of the left hand toggle mechanism is to the right of the position shown in Fig. l; and that in such "off" position of the band the angle between members I 40 and I42 of the mechanism is more acute than as shown, so that arm I40 forms the base of a triangle whose other two sides are constituted by elements I, I42. Upon reflec- 25 tion it will be seen that by pressing roller I03 to the left and holding anchorage pin la the same eiiect is obtained as would occur if roller I03 were held and pin I4Ia were pressed to the right which latter action is substan- 30 tially identical with the action, described above, of the right hand toggle mechanism of Figure i.

In each toggle mechanism seen in Fig. i there is provided a torsion spring (I50 in the left hand mechanism, ISI in the right hand mechanism of 35 Fig. l), the action of which is to tend to brake the toggle in each case, and so to maintain the corresponding brake band slack on drum 03.

The duplicate and substantially symmetrical arrangement of brake bands 80', 0|, and of the 40 control means therefor, as shown, provides a balanced assembly as regards braking torque.

It will, of course, be understood that the present invention can, with suitable modifications to the connections between the toggles and brake 45 bands, be applied as well to an internal expanding brake as to an external contracting brake.

What I claim is:

l. Self-adjusting mechanism for taking up wear in band-brakes comprising a drum, a brake- 5 band, members movable to apply said brakeband on said drum, a bipartite member capable of alteration in length by screwed adjustment of its parts, two axially separated self-lapping coil springs of opposite hand mounted one on 55 each part of said bipartite member and serving, when the brake-band becomes worn a predetermined amount to produce alteration in length of said bipartite member, upon fully applying and releasing the brake-band. o

2. Self-adjusting mechanism for taking up wear 'in band-brakes comprising a brake-band,

a substantially triangular structure formed of an inextensible member consisting of two plates held together by bridge pieces one of which piecu o5 bears against one end of said brake band, a member adjustable in length, and a strut, said strut and said adjustable member being held between the free end of said brake-band and the other of said bridge pieces. 70

e1fi 1ng mechanism for taking up wear in band-brakes comprising a brake-band, a substantially triangular structure formed of an inextensible member connected to one end of said brake-band. a bipartite memba' adjustable in 7' length, two axially separated self-lapping coil springs or opposite hand mounted one on each part of said bipartite member and serving, when the brake-band becomes worn a predetermined amount to produce alteration in length of said bipartite member, upon fully applying and releasing the brake-band, and a strut, said strut and said adjustable member being held between the free end of said brake-band and said inextensible member.

4. Self-adjusting mechanism for taking up wear in band-brakes comprising a casing, a brake-band having a gap between its ends, a substantially triangular structure formed of an inextensible member connected to one end of said brake-band, a member automatically adjustable in length anchored to said casing, and a strut, said strut and said adjustable member being held between the free end of said brakeband and said inextensible member.

5. Self-adjusting mechanism for taking up wear in band-brakes comprising a pair of brakebands each having a gap between its two ends both bands being arranged around a single drum to be braked with said gaps substantially diametrically opposite each other, aplurality of sets of members movable to apply said brake-bands substantially equally on said drum a plurality oi bipartite members capable of alteration in length by screwed adjustment of their parts, and one-way clutching means mounted on said bipartite members serving, when the brake-bands become worn a predetermined amount to produce alteration in length of said bipartite members, and consequent adjustment of said brakebands, upon fully applying and releasing the brake-bands a requisite number of times.

6. Self-adjusting mechanism Ior taking up wear in band-brakes comprising a brake-band, an anchored member, a bipartite member movable relatively thereto to apply the brake-band, said bipartite member being capable of alteration in length by screwed adjustment of its parts, two axially separated self-lapping coil springs of opposite hand mounted one on each part of said bipartite member and serving, when the brake-band becomes worn a predetermined amount to produce alteration in length of said bipartite member, upon fully applying and releasing the brake-band.

7. Self-adjusting mechanism for taking up wear in band-brakes comprising a brake-band, a bipartite anchored member, a member movable relatively thereto to apply the brake-band, said bipartite anchored member being capable of alteration in length by screwed adjustment of its parts, and two axially separated self-lapping coil springs of opposite hand mounted one on each part or said bipartite member and serving, when the brake-band becomes worn a predetermined amount to produce alteration in length of said bipartite member, upon tully applying and releasing the brake-band.

8. For use in connection with brake-band applying mechanism, self-adjusting mechanism for taking up wear, comprising a substantially triangular structure formed of aninextensible member, a member adjustable in length, a pair of self-lapping coil springs of opposite hand mounted on said adjustable member, and a strut.

9. For use in connection with band-brake applying mechanism, self-adjustingmechanism for taking up wear, comprising a substantially triangular structure formed of an inextensible member, a bipartite member adjustable in length, two axially separated self-lapping coil springs of opposite hand mounted one on each part of said bipartite member, and a strut.

l0. Selbadjusting mechanism for taking up wear in band brakes comprising a casing, a brake band comprising two spaced ends, a substantially triangular structure formed of an inextensible member connected to one end of said brake band, a member adjustable in length and carrying two axially separated seii' -1apping coil springs or opposite hand, one of said members being anchored to said casing, and a strut, said strut and said adjustable member being held between the free end of said brake band and said anchored member.

JOSEPH YOXALL. 

